<%--
  Author: cac
  Date: 2005-12-30
--%>
<%@ page contentType="image/jpeg;charset=UTF-8" %>
<%@ page import="javax.imageio.ImageIO,java.awt.*,java.awt.image.BufferedImage,java.util.Random" %>

<%
    System.setProperty("java.awt.headless", "true");

    //设置页面不缓存
    response.setHeader("Pragma", "No-cache");
    response.setHeader("Cache-Control", "no-cache");
    response.setDateHeader("Expires", 0);

    // 在内存中创建图象
    int width = 55, height = 18;
    BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);

    // 获取图形上下文
    Graphics g = image.getGraphics();

    //生成随机类
    Random random = new Random();

    // 设定背景色
    g.setColor(new Color(255, 255, 255));
    g.fillRect(0, 0, width, height);

    //设定字体
    g.setFont(new Font("Lucida Console", Font.PLAIN, 14));

    // 随机产生155条干扰线，使图象中的认证码不易被其它程序探测到
    /* g.setColor(getRandColor(160, 200));
    for (int i = 0; i < 155; i++)
    {
        int x = random.nextInt(width);
        int y = random.nextInt(height);
        int xl = random.nextInt(12);
        int yl = random.nextInt(12);
        g.drawLine(x, y, x + xl, y + yl);
    }*/

    // 取随机产生的认证码(4位数字)
    String sRand = "";
    String[] ychar = {"0" ,"1", "2", "3", "4", "5", "6", "7", "8", "9"};
    for (int i = 0; i < 4; i++)
    {
        String rand = ychar[random.nextInt(10)];
        sRand += rand;
        // 将认证码显示到图象中
        g.setColor(new Color(20 + random.nextInt(110), 20 + random.nextInt(110), 20 + random.nextInt(110)));
        //调用函数出来的颜色相同，可能是因为种子太接近，所以只能直接生成
        g.drawString(rand, 13 * i + 6, 16);
    }

    // 将认证码存入SESSION
    session.setAttribute("rand", sRand);

    // 图象生效
    g.dispose();

    //输出图象到页面
    ImageIO.write(image, "JPEG", response.getOutputStream());
    out.clear();
    out = pageContext.pushBody();
%>